What is the use of guard cells?

Guard cells are specialized cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stomatal pore. The stomatal pores are largest when water is abundant and they are smallest when it is dry.

Step 1: Understanding the Structure of Guard Cells Guard cells are bean-shaped cells covering the stomata opening. They are surrounded by two subsidiary cells and contain chloroplasts, so they can manufacture food by photosynthesis.

Step 2: Role in Gas Exchange Guard cells control the opening and closing of stomata, thus regulating the exchange of gases (oxygen and carbon dioxide) and water vapor between the outside air and the interior of the leaf.

Step 3: Role in Transpiration Guard cells play a crucial role in photosynthesis by regulating the entry of materials necessary for the process. They also help in transpiration, which is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.

Step 4: Response to Light Guard cells are sensitive to light and open during the day when light levels increase and close during the night. This helps maximize the uptake of carbon dioxide for photosynthesis while minimizing water loss.

Step 5: Role in Plant Water Regulation By opening and closing the stomata, guard cells also regulate the water balance of the plant. When the guard cells lose water, the stomata close to prevent further water loss. When they gain water, the stomata open to allow for gas exchange to continue.